34H and 36G are sister sizes — the same cup volume worn on a band that's 2 inches different, 34H being the snugger, more supportive option and 36G the looser, roomier one.
34H and 36G are sister sizes — the same cup volume worn on a band that’s 2 inches different, 34H being the snugger, more supportive option and 36G the looser, roomier one.
Plenty of women bounce between 34H and 36G for years without ever being told both fit the same body the same way.
Why 34H and 36G Hold the Same Volume
A snugger band carries more of the support load directly against your ribs, so the cup itself can be smaller. Loosen that band and the cup has to pick up the slack the band used to handle.
In practice: 34H pairs a tighter, more supportive band with a smaller cup letter, while 36G pairs a looser band with a bigger cup letter — both are carrying the identical amount of breast tissue, just distributed differently.
It also explains why a bra you loved for years can suddenly feel wrong after weight changes, pregnancy, or just time — you may have simply shifted from one of these sizes toward the other without realizing it.
Signs You Need the Snugger 34H Instead
Lean toward 34H if the band rides up in the back within an hour of putting it on. A band that isn’t doing its job shows up as strap and shoulder problems long before it shows up as an obvious “this is loose” feeling.
Signs You Need the Roomier 36G Instead
Lean toward 36G if there’s visible spillage at the top or sides of the cup by midday. Cup problems are usually easier to spot than band problems, but they get blamed on “bad luck with bra shopping” far more often than they should.
Which One Should You Try First
There’s no universal “better” choice here — brand and style matter as much as the size label. The honest answer is to try both if you can and see which band tension your ribcage actually prefers.
Not sure which of these two is actually your size? Run your measurements through the Sister Size Calculator or the Main Bra Calculator — both are free, private, and take under a minute.
Style Considerations
Full-coverage and plunge styles with real structure hold up better than soft, unlined designs at this range.
This Can Change Over Time
Body measurements can shift slightly with the seasons for some people — a bra that fit perfectly in summer can feel different after a few months, which is normal and worth a quick re-check rather than assuming something’s wrong.
Shopping Tips
Reading recent reviews that mention true-to-size feedback for the exact style (not just the brand generally) is one of the more reliable ways to predict fit before buying online.
FAQ
Not identical — the cup volume is the same, but a tighter band feels different against your ribs than a looser one. Most people have a genuine preference once they try both.
That usually means the starting measurement was slightly off rather than the sister-size logic being wrong — re-check your underbust and bust measurement with the main calculator before trying a third size.
Yes — ribcage size and tissue distribution both shift over time, so it's worth re-measuring periodically rather than assuming your old preference between these two sizes still holds.
Round toward the snugger band if you have a fuller, less bony ribcage, and toward the looser band if your ribcage is narrower or more angular — band comfort is the deciding factor, not the cup.
Yes, for most people — weight change, age, hormonal shifts, and even different laundry habits can all move the number gradually, which is why periodic re-measuring matters more than getting it right once.
Mid-morning to early afternoon tends to be most representative for most people — very early morning or late evening can show minor temporary swelling that isn't your typical baseline.
Yes — measuring while slouching or with unnatural posture can shift the numbers slightly; stand naturally with normal, relaxed posture for the most accurate result.
